Antineoplastic peptides

ABSTRACT

The present invention provides antineoplastic peptides of formula I,  
     R 1 R 2 N-CHX-CO-A-B-D-E-(G) s -K  I 
     wherein R 1 , R 2 , X, A, B, D, E, G, K and s have the meanings stated in the description. The compounds have antineoplastic activity.

RELATED APPLICATIONS

[0001] This application is a continuation of application Ser. No. 09/097,184, filed Jun. 12, 1998, which is a continuation-in-part of International Application No. PCT/EP96/05518, filed Dec. 11, 1996, which designated the United States, published in English, which claims priority to U.S. patent application No. 08/573,422, filed Dec. 15, 1995, now abandoned. This application also claims benefit of U.S. Provisional Application entitled “Antineoplastic Peptides”, which resulted from the conversion of U.S. Ser. No. 08/573,422.

[0002] The entire teachings of the above application(s) are incorporated herein by reference.

FIELD OF THE INVENTION

[0003] The invention described herein provides novel peptides and derivatives thereof which offer potentially improved therapeutic utilities for the treatment of neoplastic diseases as compared to dolastatin −10 and −15 (U.S. Pat. Nos. 4,879,276 and 4,816,444) and the compounds desribed in WO 93/23424.

SUMMARY OF THE INVENTION

[0004] Compounds of this invention include novel peptides of the formula I

R¹R²N-CHX-CO-A-B-D-E-(G)_(s)-K  I

[0005] where

[0006] R¹ is hydrogen, methyl, or ethyl;

[0007] R² is methyl; or ethyl; or

[0008] R¹-N-R² together are a pyrrolidine ring;

[0009] A is a valyl, isoleucyl, allo-isoleucyl, 2-tert-butylglycyl, 2-ethylglycyl, norleucyl or norvalyl residue;

[0010] B is a N-methyl-valyl, N-methyl-norvalyl, N-methyl-leucyl, N-methyl-isoleucyl, N-methyl-2-tert-butylglycyl, N-methyl-2-ethylglycyl, or N-methyl-norleucyl residue;

[0011] D is a prolyl, homoprolyl, hydroxyprolyl, or thiazolidine-4-carbonyl residue;

[0012] E is a prolyl, homoprolyl, hydroxyprolyl, thiazolidine-4-carbonyl, trans-4-fluoro-L-prolyl, cis-4-fluoro-L-prolyl, trans-4-chloro-L-prolyl or cis-4-chloro-L-prolyl residue;

[0013] X is ethyl, propyl, butyl, isopropyl, sec. butyl, tert.-butyl, cyclopropyl, or cyclopentyl;

[0014] G is a L-2-tert.butylglycyl, D-2-terr.butylglycyl, D-valyl, D-isoleucyl, D-leucyl, D-norvalyl, 1-aminopentyl-1-carbonyl, or 2,2-dimethylglycyl residue;

[0015] s is 0 or 1;

[0016] K is —NH-C₁₋₈-alkyl, —NH-C₃₋₈-alkenyl, —NH-C₃₋₈-alkinyl, —NH-C₆₋₈-cycloalkyl, —NH-C₁₋₄-alkene-C₃₋₈-cycloalkyl, C₁₋₄-alkyl-N-C ₁₋₆-alkyl, in which residues one CH₂ group may be replaced by O or S, one H by phenyl or cyano, or 1, 2 or 3 H by F, except the N-methoxy-N-methylamino, N-benzylamino, or N-methyl-N-benzylamino residue, or K is

[0017] and the salts thereof with physiologically tolerated acids.

DETAILED DESCRIPTION OF THE INVENTION

[0018] In specific embodiments of the compounds of formula I, K may be —NHCH₃, —NHCH₂CH₃, —NH(CH₂)₂CH₃, —NH(CH₂)₃CH₃, —NH(CH₂)₄CH₃, —NH(CH₂)₅CH₃, —NH(CH₂)₆CH₃, —NHCH(CH₂)₇CH₃, —NHCH(CH₃)₂, —NHCH(CH₃)CH₂CH₃, —NHCH(CH₂CH₃)₂, —NHCH(CH₂CH₂CH₃) ₂, —NHC(CH₃)₃, —NHCH(CH₂CH₃)CH₂CH₂CH₃, —NHCH(CH₃)CH(CH₃)₂, —NHCH(CH ₂CH₃)CH(CH₃)₂, —NHCH(CH₃)C(CH₃)₃, —NH-cyclohexyl, —NH-cycloheptyl, —NH-cyclooctyl, —N(CH₃)OCH₂CH₃, —N(CH₃)OCH₂CH₂CH₃, —N(CH₃)OCH(CH₃)₂, —N(CH₃)O(CH₂)₃CH₃, —N(CH₃)OCH₂C₆H₅, —NH(CH₂)₂C₆H₅, —NH(CH₂)₃C₆H₅, —NHCH(CH₃)C₆H₅, —NHC(CH₃)₂C₆H₅, —NHC(CH₃)₂CH₂CH₃, —NHC(CH₃)(CH₂CH₃)₂, —NHCH[CH(CH₃)₂]₂, —NHC(CH₃)₂CN, —NHCH(CH₃)CH(OH)C₆H₅, —NHCH₂-cyclohexyl, —NHCH₂C(CH₃)₃, —NHCH₂CH(CH₃)₂, —N(CH₃)₂, —N(CH₂CH₃)₂, —N(CH₂CH₂CH₃)₂, —NHCH₂CF₃, —NHCH(CH₂F)₂, —NHCH₂CH₂F, —NHCH₂CH₂OCH₃, —NHCH₂CH₂SCH₃, —NHCH₂CHCH₂, —NH-C(CH₃)₂CH═CH₂, —NHC(CH₃)₂C≡CH, —NHC(CH₂CH₃)₂C≡CH, —NHC(CH₃)₂CH₂CH₂OH, —NH(CH₂CH₂O)₂CH₂CH₃, —NHC(CH₃)₂CH(CH₃)₂, —NHC(CH₃)₂CH₂CH₂CH₃, —NHC(CH₃) ₂CH₂C₆H₅, —N(OCH₃)CH(CH₃)₂, —N(OCH₃)CH₂CH₃, —N(OCH₃)CH₂CH₂CH₃, —N(OCH₃)CH₂C₆H₅, —N(OCH₃)C₆H₅, —N(CH₃)OC₆H₅, —NHCH[CH(CH₃)₂]₂, —N(OCH₃)CH₂CH₂CH₂CH₃, or the special ring systems mentioned above.

[0019] In one embodiment of the compounds of formula I described above, s is 0 and E is homoprolyl or hydroxyprolyl.

[0020] Preferred are compounds of the formula I where the substituents R¹, R², A, B, D, E, X, G and s have the following meanings:

[0021] R¹ hydrogen, methyl, or ethyl, especially methyl;

[0022] R² methyl or ethyl, especially methyl;

[0023] A valyl, isoleucyl, 2-tert-butylglycyl, 2-ethylglycyl, norleucyl or norvalyl, especially valyl, isoleucyl, 2-tert-butylglycyl, 2-ethylglycyl,

[0024] B N-methyl-valyl, N-methyl-norvalyl, N-methyl-isoleucyl, N-methyl-2-tert-butylglycyl, N-methyl-2-ethylglycyl, or N-methyl-norleucyl, especially N-methyl-valyl, N-methyl-2-ethylglycyl, N-methyl-norleucyl, N-methyl-isoleucyl, or N-methyl-2-tert.butyl-glycyl;

[0025] D prolyl, homoprolyl or thiazolidine-4-carbonyl, especially prolyl or thiazolidine-4-carbonyl;

[0026] E prolyl, homoprolyl, thiazolidine-4-carbonyl, trans-4-fluoro-L-prolyl, cis-4-fluoro-L-prolyl, trans-4-chloro-L-prolyl or cis-4-chloro-L-prolyl, especially prolyl, trans-4-fluoro-prolyl, cis-4-fluoro-prolyl, trans-4-chloro-prolyl, or cis-4-chloro-prolyl;

[0027] X ethyl, propyl, isopropyl, sec.butyl, tert.butyl or cyclo-propyl, especially ethyl, isopropyl, sec.butyl or tert.butyl;

[0028] G L-2-tert.butylglycyl, D-2-tert.butylglycyl, D-valyl, D-isoleucyl, D-leucyl or 2,2-dimethylglycyl residue;

[0029] s 0 or 1.

[0030] Preferred meanings for K are:

[0031] —NH-C₁₋₈-alkyl, 'NH-C₆₋₈-cycloalkyl, —NH-CH₂-cyclohexyl, C₁₋₄-alkyl-N-C₁₋₆-alkyl, in which residues one CH₂ group may be replaced by O, one H by phenyl or 1 or 2 H by F, except the N-methoxy-N-methylamino, N-benzylamino, or N-methyl-N-benzylamino residue, or K is

[0032] More preferred K is —NHCH₃, —NHCH₂CH₃, —NH(CH₂)₂CH₃, —NH(CH₂)₃CH₃, —NH(CH₂)₄CH₃, —NH(CH₂)₅CH₃, —NH(CH₂)₆CH₃, — NH(CH₂)₇CH₃, —NHCH(CH₃)₂, —NHCH(CH₃)CH₂CH₃, —NHCH(CH₂CH₃)₂, —NHCH(CH₂CH₂CH₃)₂, —NHC(CH₃)₃, —NHCH(CH₂CH₃)CH₂CH₂CH₃, —NHCH(CH₃)CH(CH₃)₂, —NHCH(CH₂CH₃)CH(CH₃)₂, —NHCH(CH₃)C(CH₃)₃, —NH-cyclohexyl, —NH-cycloheptyl, —NH-cyclooctyl, —N(CH₃)OCH₂CH₃, —N(CH₃)OCH₂CH₂CH₃, —N(CH₃)OCH(CH₃)₂, —N(OCH₃)CH(CH₃)₂, —N(CH₃)OCH₂C₆H₅, —NH(CH₂)₂C₆H₅, —NH(CH₂)₃C₆H₅, —NHCH(CH₃)C₆H₅, —NHC(CH₃)₂C₆H₅, —NHC(CH₃)₂CH₂CH₃, —NHC(CH₃)(CH₂CH₃)₂, —NHCH(CH₃)CH(OH)C₆H₅, —NHCH₂-cyclohexyl, —N(CH₃)₂, —N(CH₂CH₃)₂, —N(CH₂CH₂CH₃)₂, —NHCH(CH₂F)₂, —NHC(CH₃)CH≡CH₂, —NHC(CH₃)₂CN, —NHC(CH₃)₂C═CH, —NHC(CH₃)₂CONH₂, —NHCH[CH(CH₃)₂]₂, —N(OCH₃)CH₂C₆H₅, —N(OCH₃)CH₂CH₃, —N(OCH₃)CH₂CH₂CH₃, —N(OCH₃)CH₂CH₂CH₂CH₃,

[0033] In one embodiment of the preferred compounds of formula I described above, s is 0 and E is homoprolyl or hydroxyprolyl.

[0034] Especially preferred are compounds of the formula I where

[0035] R¹ and R² are methyl,

[0036] A is a valyl, isoleucyl, 2-tert.-butylglycyl residue

[0037] B is a N-methylvalyl, N-methyl-isoleucyl, N-methyl-2-tert.-butylglycyl residue,

[0038] D is a prolyl or thiazolidine-4-carbonyl residue,

[0039] E is a prolyl, cis-4-fluoro-L-prolyl, or cis-4-chloro-L-prolyl residue,

[0040] X is a isopropyl, sec.-butyl, or tert.-butyl residue,

[0041] s is 0, and

[0042] K is —NHCH(CH₃)₂, —NHCH(CH₃)CH₂CH₃, —NHCH(CH₂CH₃)₂, —NHCH(CH₂CH₂CH₃)₂, —NHC(CH₃)₃, —NHCH(CH₂CH₃)CH₂CH₂CH₃, —NHCH(CH₃)CH(CH₃)₂, —NHCH(CH₂CH₃)CH(CH₃)₂, —NHCH(CH₃)C(CH₃)₃, —NH-cycloheptyl, —NH-cyclooctyl, —N(CH₃)OCH₂CH₃, —N(CH₃)OCH₂CH₂CH₃, —N(CH₃)OCH(CH₃)₂, —N(OCH₃)CH(CH₃)₂, —N(CH₃)OCH₂C₆H₅, —NH(CH₂)₂C₆H₅, —NH(CH₂)₃C₆H₅, —NHCH(CH₃)C₆H₅, —NHC(CH₃)₂C₆H₅, —NHC(CH₃)₂CH₂CH₃, —NHC(CH₃)(CH₂CH₃)₂, —NHCH(CH₃)CH(OH)C₆H₅, —NHCH(CH₂F)₂, —NHC(CH₃)₂CH₂CH₂OH, —NH(CH₂CH₂O)₂CH₂CH₃, —NHC(CH₃)₂CH═CH₂, —NHC(CH₃)₂CH(CH₃)₂, —N(OCH₃)CH₂CH₃, —N(OCH₃)CH₂CH₂CH₃, —N(OCH₃)CH₂CH₂CH₂CH₃, —NHC(Ch₃)₂CN, —NHC(CH₃)₂C≡CH, —NHCH[CH(CH₃)₂]₂, —NHC(CH₃)₂CONH₂, —NHC(CH₃)₂CH₂C₆H₅, —N(OCH₃)C₆H₅, —N(OCH₃)CH₂C₆H₅,

[0043] This invention also provides methods for preparing the compounds of formula I, pharmaceutical compositions containing such compounds together with a pharmaceutically acceptable carrier and methods for using same for treating cancer in mammals.

[0044] The new compounds may be present as salts with physiologically tolerated acids such as: hydrochloric acid, citric acid, tartaric acid, lactic acid, phosphoric acid, methanesulfonic acid, acetic acid, formic acid, maleic acid, fumaric acid, malic acid, succinic acid, malonic acid, sulfuric acid, L-glutamic acid, L-aspartic acid, pyruvic acid, mucic acid, benzoic acid, glucuronic acid, oxalic acid, ascorbic acid and acetylglycine.

[0045] The novel compounds can be prepared by known methods of peptide chemistry. Thus, the peptides can be assembled sequentially from amino acids or by linking suitable small peptide fragments. In the sequential assemblage, starting at the C terminus the peptide chain is extended stepwise by one amino acid each time. In fragment coupling it is possible to link together fragments of different lengths, and the fragments in turn can be obtained by sequential assemblage from amino acids or themselves by fragment-coupling.

[0046] Both in the sequential assemblage and in the fragment coupling it is necessary to link the units by forming an amide linkage. Enzymatic and chemical methods are suitable for this.

[0047] Chemical methods for forming the amide linkage are described in detail by Mueller, Methoden der organischen Chemie Vol. XV/2, pp 1 to 264, Thieme Verlag, Stuttgart, 1974; Stewart, Young, Solid Phase Peptide Synthesis, pp 31 to 34, 71 to 82, Pierce Chemical Company, Rockford, 1984; Bodanszky, Klausner, Ondetti, Peptide Synthesis, pp 85 to 128, John Wiley & Sons, New York, 1976; The Practice of Peptide Synthesis, M. Bodanszky, A. Bodanszky, Springer-Verlag, 1994, and other standard works on peptide chemistry. Particular preference is given to the azide method, the symmetric and mixed anhydride method, in situ generated or preformed active esters, the use of urethane protected N-carboxy anhydrides of amino acids and the formation of the amide linkage using coupling reagents, especially dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide (DIC), 1-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), pivaloylchloride, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDCI), n-propanephosphonic anhydride (PPA), N,N-bis(2-oxo-3-oxazolodinyl)-amidophosphoryl chloride (BOP-C1), bromo-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBrop), diphenylphosphoryl azide (DPPA), Castro's reagent (BOP, PyBop), O-benzotriazolyl-N,N,N′,N′-tetramethyluronium salts (HBTU), O-azabenzotriazolyl-N,N,N′,N′-tetramethyluronium salts (HATU), diethylphosphoryl cyanide (DEPCN), 2,5-diphenyl-2,3-dihydro-3-oxo-4-hydroxythiophene dioxide (Steglich's reagent; HOTDO) and 1,1′-carbonyldiimidazole (CDI). The coupling reagents can be employed alone or in combination with additives such as N,N-dimethyl-4-aminopyridine (DMAP), N-hydroxy-benzotriazole (HOBt), N-hydroxybenzotriazine (HOOBt), Azabenzotriazole, N-hydroxysuccinimide (HOSu) or 2-hydroxypyridine.

[0048] Whereas it is normally possible to dispense with protective groups in enzymatic peptide synthesis, reversible protection of reactive groups not involved in formation of the amide linkage is necessary for both reactants in chemical synthesis. Three conventional protective group techniques are preferred for the chemical peptide synthesis: the benzyloxycarbonyl (Z), the t-butoxycarbonyl (Boc) and the 9-fluorenylmethoxycarbonyl (Fmoc) techniques.

[0049] Identified in each case is the protective group on the alpha-amino group of the chain-extending unit. A detailed review of amino-acid protective groups is given by Mueller, Methoden der organischem Chemie vol. XV/1, pp 20 to 906, Thieme Verlag, Stuttgart, 1974. The units employed for assembling the peptide chain can be reacted in solution, in suspension or by a method similar to that described by Merrifield in J. Amer. Chem. Soc. 85 (1963) 2149.

[0050] Suitable for peptide synthesis in solution are all solvents which are inert under the reaction conditions, especially water, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, dichloromethane (DCM), ethyl acetate, 1,4-dioxane, tetrahydrofuran (THF), N-methyl-2-pyrrolidone (NMP) and mixtures of the said solvents.

[0051] Peptide synthesis on the polymeric support can be carried out in all inert organic solvents in which the amino-acid derivatives used are soluble. However, preferred solvents additionally have resin-swelling properties, such as DMF, DCM, NMP, acetonitrile and DMSO, and mixtures of these solvents. After synthesis is complete, the peptide is cleaved off the polymeric support. The conditions under which cleavage off the various resin types is possible are disclosed in the literature. The cleavage reactions most commonly used are acid- and palladium-catalyzed, especially cleavage in liquid anhydrous hydrogen fluoride, in anhydrous trifluoromethanesulfonic acid, in dilute or concentrated trifluoroacetic acid, palladium-catalyzed cleavage in THF or THF-DCM mixtures in the presence of a weak base such as morpholine or cleavage in acetic acid/dichloromethane/trifluoroethanol mixtures. Depending on the chosen protective groups, these may be retained or likewise cleaved off under the cleavage conditions.

[0052] Partial deprotection of the peptide may also be worthwhile when certain derivatization reactions are to be carried out.

[0053] Peptides dialkylated at the N-terminus can be prepared either by coupling on the appropriate N,N-di-alkylamino acids in solution or on the polymeric support, by reductive alkylation of the resin-bound peptide in DMF/1% acetic acid with NaCNBH₃ and the appropriate aldehydes, by hydrogenation of the peptide in solution in the presence of aldehyde or ketone and Pd/C.

[0054] The various non-naturally occurring amino acids as well as the various non-amino acid moieties disclosed herein may be obtained from commercial sources or synthesized from commercially-available materials using methods known in the art. For example, amino acids building blocks with R¹ and R² moieties can be prepared according to E. Wuensch, Houben Weyl, Meth. d. Org. Chemie, Bd. XV, 1, p. 306 following, Thieme Verlag Stuttgart 1974 and Literature cited therein.

[0055] The compounds of this invention may be used to inhibit or otherwise treat solid tumors (e.g. tumors of the lung, breast, colon, prostate, bladder, rectum, or endometrial tumors) or hematological malignancies (e.g. leukemias, lymphomas) by administration of the compound to the mammal.

[0056] It is a special advantage of the new compounds that they are very resistant to enzymatic degradation and can also be administered orally.

[0057] Administration may be by any of the means which are conventional for pharmaceutical, preferably oncological, agents, including oral and parenteral means such as subcutaneously, intravenously, intramuscularly and intraperitoneally.

[0058] The compounds may be administered alone or in the form of pharmaceutical compositions containing a compound of formula I together with a pharmaceutically accepted carrier appropriate for the desired route of administration. Such pharmaceutical compositions may be combination products, i.e., may also contain other therapeutically active ingredients.

[0059] The dosage to be administered to the mammal with contain an effective tumor-inhibiting amount of active ingredient which will depend upon conventional factors including the biological activity of the particular compound employed; the means of administration; the age, health and body weight of the recipient; the nature and extent of the symptoms; the frequency of treatment; the administration of other therapies; and the effect desired. A typical daily dose will be about 0.05 to 50 milligrams per kilogram of body weight on oral administration and about 0.01 to 20 milligrams per kilogram of body weight on parenteral administration.

[0060] The novel compounds can be administered in conventional solid or liquid pharmaceutical administration forms, e.g. uncoated or (film-)coated tablets, capsules, powders, granules, suppositories or solutions. These are produced in a conventional manner. The active substances can for this purpose be processed with conventional pharmaceutical aids such as tablet binders, fillers preservatives, tablet disintegrants, flow regulators, plasticizers, wetting agents, dispersants, emulsifiers, solvents, sustained release compositions, antioxidants and/or propellant gases (cf. H. Sucker et al.: Pharmazeutische Technologie, Thieme-Verlag, Stuttgart, 1978). The administration forms obtained in this way normally contain 1-90% by weight of the active substance.

[0061] The following examples are intended to illustrate the invention. The proteinogenous amino acids are abbreviated in the examples using the known three-letter code. Other abbreviations used: Me₂Val=N,N-dimethylvaline, MeVal= N-methylvaline.

EXAMPLES

[0062] A. General Procedures

[0063] I. The peptides claimed in claim 1 are either synthesized by classical solution synthesis using standard Z- and Boc-methodology as described above or by standard methods of solid-phase synthesis using Boc and Fmoc protective group techniques.

[0064] In the case of solid phase synthesis, the N,N-dialkylpenta- or hexapeptide acids are liberated from the solid support and further coupled with the corresponding C-terminal amines in solution. BOP-C1 and PyBrop were used as reagents for coupling of the amino acid following the N-methylamino acids. The reaction times were correspondingly increased. For reductive alkylation of the N-terminus, the peptide-resin was deprotected at the N terminus and then reacted with a 3-fold molar excess of aldehyde or ketone in DMF/1% acetic acid with addition of 3 equivalents of NaCNBH₃. After the reaction was complete (negative Kaisertest) the resin was washed several times with water, isopropanol, DMF and dichloromethane.

[0065] In solution synthesis, the use of either Boc-protected amino acid NCAs (N-tert.-butyloxycarbonyl-amino acid-N-carboxy-anhydrides), Z-protected amino acid NCAs (N-benzyloxycarbonyl-amino acid-N-carboxy-anhydrides), or the use of pivaloylchloride as condensing agent respectively is most advantageous for coupling of the amino acid following the N-methylamino acids. Reductive alkylation of the N terminus can e.g. be achieved by reaction of the N-terminally deprotected peptides or amino acids with the corresponding aldehydes or ketones using NaCNBH₃ or hydrogen, Pd/C.

[0066] II. Purification and characterization of the peptides

[0067] Purification was carried out by gel chromatography (SEPHADEX G-10, G-15/10% HOAc, SEPHADEX LH20/MeOH), medium pressure chromatography (stationary phase: HD-SIL C-18, 20-45 mikron, 100 Angstrom; mobile phase: gradient with A=0.1% TFA/MeOH, B=0.1% TFA/water), or preparative HPLC (stationary phase: Waters Delta-Pak C-18, 15 mikron, 100 Angstrom; mobile phase: gradient with A=0.1% TFA/MeOH, 3=0.1% TFA/water).

[0068] The purity of the resulting products was determined by analytical HPLC (stationary phase: 100 2.1 mm VYDAC C-18, 5 1, 300 A; mobile phase: acetonitrile-water gradient, buffered with 0.1% TFA, 40° C.).

[0069] Characterization was by amino-acid analysis and fast atom bombardment mass spectroscopy.

[0070] B. Specific Procedures

Example 1 (SEQ ID NO: 1) Me₂Val-Val-MeVal-Pro-Pro-NHCH(CH₃)₂

[0071] a) Z-MeVal-Pro-OME

[0072] 66.25 g (250 mmol) Z-MeVal-OH were dissolved in 250 ml dry dichloromethane. After addition of 36.41 ml (262.5 mmol) triethylamine, the reaction mixture was cooled to −25° C. and 32.27 ml (262.5 mmol) pivaloyl chloride were added. After stirring for 2,5 h, 41.89 g (250 mmol) H-Pro-OMe×Chl in 250 ml dichloromethane, neutralized with 36.41 ml (262.5 mmol) triethylamine at 0° C., were added to the reaction mixture. Stirring continued for 2 h at −25° C. and overnight at room temperature. The reaction mixture was diluted with dichloromethane and thoroughly washed with saturated aqueous NaHCO₃ solution (3x), water (1x), 5% citric acid (3x) and saturated NaCl solution. The organic phase was dried over sodium sulfate and evaporated to dryness. The residue (91.24 g) was stirred with petroleum ether overnight and filtered. 62.3 g of product were obtained.

[0073] b) H-MeVal-Pro-OMe

[0074] 48.9 g (130 mmol) Z-MeVal-Pro-OMe were dissolved in 490 ml methanol. After addition of 10.9 ml (130 mmol) concentrated hydrochloric acid and 2.32 g 10% Palladium/charcoal, the reaction mixture was hydrogenated. Filtration and evaporation to dryness yielded 36.32 g of the product.

[0075] c) Z-Val-MeVal-Pro-OMe

[0076] 18.1 g (65 mmol) H-MeVal-Pro-OMe, 21.6 g (78 mmol) Z-Val-N-carboxyanhydride and 22.8 ml (130 mmol) diisopropylethylamine were stirred in 110 ml DMF at 40° C. for 2 d. After evaporation of DMF, dichloromethane was added and the organic phase washed with saturated aqueous NaHCO₃ solution (3x), water (1x), 4% citric acid (3X) and saturated NaCl solution. The organic phase was dried over sodium sulfate and evaporated to dryness. The product (29.3 g) was obtained as a viscous oil.

[0077] d) H-Val-MeVal-Pro-OMe

[0078] 29.3 g (61.6 mmol) of Z-Val-MeVal-Pro-OMe were dissolved in 230 ml methanol. After addition of 1.15 g 10% Palladium/charcoal, the reaction mixture was hydrogenated. Filtration and evaporation to dryness yielded 21.96 g of the product.

[0079] e) Z-Val-Val-MeVal-Pro-OMe

[0080] 15.29 g (61 mmol) Z-Val-OH and 21.96 g (61 mmol) H-Val-MeVal-Pro-OMe were dissolved in 610 ml dichloromethane and cooled to 0° C. After addition of 8.16 ml (73.2 mmol) N-Methylmorpholine, 2.77 g (20.3 mmol) HOBt and 11.73 g (61 mmol) EDCI, the reaction mixture was stirred overnight at room temperature, diluted with dichloromethane and thoroughly washed with saturated aqueous NaHCO₃ solution (3x), water (1x), 5% citric acid (3X) and saturated NaCl solution. The organic phase was dried over sodium sulfate and evaporated to dryness to yield 31.96 g of the product.

[0081] f) Z-Val-Val-MeVal-Pro-OH

[0082] 31.96 g (57 mmol) Z-Val-Val-MeVal-Pro-OMe were dissolved in 250 ml methanol. 102.6 ml of a 1 N LiOH solution was added and the mixture stirred overnight at room temperature. After addition of 500 ml water, the aqueous phase was washed three times with ethyl acetate, adjusted to pH 2 at 0° C. and extracted three times with ethyl acetate. The organic phase was dried over sodium sulfate and evaporated to dryness yielding 30.62 g of the desired product as a white solid.

[0083] g) Z-Val-Val-MeVal-Pro-Pro-NHCH(CH₃)₂

[0084] 2 g (3.35 mmol) Z-Val-Val-MeVal-Pro-OH and 0.664 g (3.35 mmol) H-Pro-NHCH(CH₃)₂ were dissolved in 34 ml of dry dichloromethane. After cooling to 0° C., 1.35 ml (12.1 mmol) N-methyhnorpholine, 0.114 g (0.84 mmol) HOBt and 0.645 g (3.35 mmol) EDCI were added and the reaction mixture stirred overnight at room temperature. 80 ml dichloromethane were added and the organic phase thoroughly washed with saturated aqueous NaHCO₃ solution (3x), water (1x), 5% citric acid (3x) and saturated NaCl solution (1x). The organic phase was dried over sodium sulfate and evaporated to dryness to yield 1.96 g of the product which was used in the next reaction without further purification.

[0085] h) Me₂Val-Val-MeVal-Pro-Pro-NHCH(CH₃)₂

[0086] 1.96 g Z-Val-Val-MeVal-Pro-Pro-NHCH(CH₃)₂ were dissolved in 11 ml methanol. 0.054 g 10% Pd/C were added under nitrogen atmosphere and the reaction mixture hydrogenated at room temperature for 4 h. After addition of 0.86 ml (11.24 mmol) of a 37% aqueous formaldehyde solution and 0.281 g 10% Pd/C, hydrogenation was continued for 5 h. Filtration and evaporation of the solvent gave rise to 2.77 g of crude product. Further purification was achieved by dissolving the peptide in water, adjusting the pH to 2 and extracting the aqueous phase three times with ethyl acetate. The aqueous phase was then adjusted to pH 8-9 and extrcted four times with dichloromethane. The organic phase was dried over sodium sulfate to yhield 1.37 g of purified product as a white foam. The compound was further purified using medium pressure liquid chromatography (10-50% A in 10 min.; 50-90% A in 320 min.). Fractions containing the product were combined, lyophilized, redissolved in water and the pH adjusted to 9 with 1 N LiOH. After extraction with dichloromethane, the organic phase was dried over sodium sulfate and evaporated to dryness. Lyophilization led to 500 mg of pure product, which was characterized by fast atom bombardment mass spectrometry ([M+H]⁺=593).

Example 2 (SEQ ID NO: 1) Me₂Val-Val-MeVal-Pro-Pro-NHC(CH₃)₃

[0087] i) Z-Val-Val-MeVal-Pro-Pro-NHC(CH₃)₃

[0088] 2 g (3.35 mmol) Z-Val-Val-MeVal-Pro-OH and 0.692 g (3.35 mmol) H-Pro-NHC (CH₃)₃ were dissolved in 34 ml of dry dichloromethane. After cooling to 0° C., 1.35 ml (12.1 mmol) N-methylmorpholine, 0.114 g (0.84 mmol) HOBt and 0.645 g (3.35 mmol) EDCI were added and the reaction mixture stirred overnight at room temperature. 80 ml dichloromethane were added and the organic phase thoroughly washed with saturated aqueous NaHCO₃ solution (3x), water (1x), 5% citric acid (3x) and saturated NaCl solution (1x). The organic phase was dried over sodium sulfate and evaporated to dryness to yield 1.8 g of the product which was used in the next reaction without further purification.

[0089] k) Me₂Val-Val-MeVal-Pro-Pro-NHC(CH₃)₃

[0090] 1.8 g Z-Val-Val-MeVal-Pro-Pro-NHC(CH₃)₃ were dissolved in 10 ml methanol. 0.049 g 10% Pd/C were added under nitrogen atmosphere and the reaction mixture hydrogenated at room temperature for 4 h. After addition of 0.86 ml (11.24 mmol) of a 37% aqueous formaldehyde solution and 0.252 g 10% Pd/C, hydrogenation was continued for 5 h. Filtration and evaporation of the solvent gave rise to 1.82 g of crude product. The compound was further purified using medium pressure liquid chromatography 910-50% A in 10 min.; 50-90% A in 320 min.). Fractions containing the product were combined, lyophilized, redissolved in water and the pH adjusted to 9 with 1 N LiOH. After extraction with dichloromethane, the organic phase was dried over sodium sulfate and evaporated to dryness. Lyophilization led to 547 mg of pure product, which was characterized by fast atom bombardment mass spectrometry ([M+H]⁺32 607).

[0091] The following compounds were prepared or can be prepared according to examples 1 and 2:

[0092] 3. Xaa Val Xab Pro Xac

[0093] 4. Xaa Val Xab Pro Xad

[0094] 5. Xaa Val Xab Pro Xae

[0095] 6. Xaa Val Xab Pro Xaf

[0096] 7. Xaa Val Xab Pro Xag

[0097] 8. Xaa Val Xab Pro Xah

[0098] 9. Xaa Val Xab Pro Xai

[0099] 10. Xaa Val Xab Pro Xak

[0100] 11. Xaa Val Xab Pro Xal

[0101] 12. Xaa Val Xab Pro Xam

[0102] 13. Xaa Val Xab Pro Xan

[0103] 14. Xaa Val Xab Pro Xao

[0104] 15. Xaa Val Xab Pro Xap

[0105] 16. Xaa Val Xab Pro Xaq

[0106] 17. Xaa Val Xab Pro Xar

[0107] 18. Xaa Val Xab Pro Xas

[0108] 19. Xaa Val Xab Pro Xat

[0109] 20. Xaa Val Xab Pro Xau

[0110] 21. Xaa Val Xab Pro Xav

[0111] 22. Xaa Val Xab Pro Xaw

[0112] 23. Xaa Val Xab Pro Xax

[0113] 24. Xdd Val Xab Pro Xay

[0114] 25. Xaa Val Xab Pro Xaz

[0115] 26. Xaa Val Xab Pro Xba

[0116] 27. Xaa Val Xab Pro Xbb

[0117] 28. Xaa Val Xbc Pro Xay

[0118] 29. Xaa Val Xab Pro Xbd

[0119] 30. Xaa Val Xab Pro Xbe

[0120] 31. Xaa Val Xab Pro Xbf

[0121] 32. Xaa Val Xab Pro Xbg

[0122] 33. Xaa Val Xab Pro Xbh

[0123] 34. Xaa Val Xab Pro Xbi

[0124] 35. Xaa Val Xab Pro Xbk

[0125] 36. Xaa Val Xab Pro Xbl

[0126] 37. Xaa Val Xab Pro Xbm

[0127] 38. Xaa Val Xab Pro Xbn

[0128] 39. Xaa Val Xab Pro Xbo

[0129] 40. Xaa Val Xab Pro Xbp

[0130] 41. Xaa Val Xab Pro Xbq

[0131] 42. Xaa Val Xab Pro Xbr

[0132] 43. Xaa Val Xab Pro Xbs

[0133] 44. Xaa Val Xab Pro Xbt

[0134] 45. Xaa Val Xab Pro Xbu

[0135] 46. Xaa Val Xab Pro Xbv

[0136] 47. Xaa Val Xab Pro Xbw

[0137] 48. Xaa Val Xab Pro Xbx

[0138] 49. Xaa Val Xab Pro Xby

[0139] 50. Xaa Val Xab Pro Xbz

[0140] 51. Xaa Val Xab Pro Xca

[0141] 52. Xaa Val Xab Pro Xcb

[0142] 53. Xaa Val Xab Pro Xcc

[0143] 54. Xaa Val Xab Pro Xcd

[0144] 55. Xaa Val Xab Pro Xce

[0145] 56. Xaa Val Xab Pro Xcf

[0146] 57. Xaa Xdf Xab Pro Xay

[0147] 58. Xaa Val Xab Pro Xch

[0148] 59. Xaa Val Xab Pro Xci

[0149] 60. Xaa Val Xab Pro Xck

[0150] 61. Xaa Val Xab Pro Xcl

[0151] 62. Xaa Val Xab Pro Xcm

[0152] 63. Xaa Val Xab Pro Xcn

[0153] 64. Xaa Val Xab Pro Xco

[0154] 65. Xaa Val Xab Pro Xcp

[0155] 66. Xaa Val Xab Pro Xcq

[0156] 67. Xaa Val Xab Pro Xcr

[0157] 68. Xaa Val Xab Pro Xcs

[0158] 69. Xaa Val Xab Pro Xct

[0159] 70. Xaa Val Xab Pro Xcu

[0160] 71. Xcw Val Xab Pro Xcv

[0161] 72. Xcx Val Xab Pro Xcv

[0162] 73. Xaa Val Xab Pro Pro Xcy

[0163] 74. Xaa Val Xab Pro Pro Xcz

[0164] 75. Xaa Val Xda Pro Xcv

[0165] 76. Xaa Xdb Xab Pro Xcv

[0166] 77. Xdc Val Xab Pro Xcv

[0167] 78. Xaa Ile Xab Pro Xcv

[0168] 79. Xdd Val Xab Pro Xcv

[0169] 80. Xde Val Xab Pro Xcv

[0170] 81. Xaa Xdf Xab Pro Xcv

[0171] 82. Xaa Val Xab Pro Xcg

[0172] 83. Xaa Val Xab Pro Pro Xdg

[0173] 84. Xaa Val Xab Pro Pro Xdh

[0174] 85. Xaa Val Xab Pro Pro Xdi

[0175] 86. Xaa Val Xab Pro Pro Xdk

[0176] 87. Xaa Val Xdl Pro Xcv

[0177] 88. Xde Val Xab Pro Xay

[0178] 89. Xaa Val Xdl Pro Xay

[0179] 90. Xaa Val Xab Pro Xdm

[0180] 91. Xaa Val Xab Pro Xdn

[0181] 92. Xaa Val Xab Pro Xdo

[0182] 93. Xaa Val Xab Pro Xdp

[0183] 94. Xaa Val Xab Pro Xdq

[0184] 95. Xaa Val Xab Pro Pro Xdr

[0185] 96. Xaa Val Xab Pro Xds

[0186] 97. Xaa Val Xbc Pro Xcv

[0187] 98. Xaa Ile Xab Pro Xay

[0188] 99. Xcw Val Xab Pro Xay

[0189] 100. Xaa Val Xbc Pro Xal

[0190] 101. Xaa Val Xdl Pro Xal

[0191] 102. Xaa Xdf Xab Pro Xal

[0192] 103. Xaa Ile Xab Pro Xal

[0193] 104. Xdd Val Xab Pro Xal

[0194] 105. Xde Val Xab Pro Xal

[0195] 106. Xcx Val Xab Pro Xcy

[0196] 107. Xcw Val Xab Pro Xal

[0197] 108. Xcx Val Xab Pro Xal

[0198] 109. Xcw Val Xab Pro Xav

[0199] 110. Xcx Val Xab Pro Xav

[0200] 111. Xcw Val Xab Pro Xaw

[0201] 112. Xcx Val Xab Pro Xaw

[0202] 113. Xab Val Xab Pro Xay

[0203] 114. Xab Val Xab Pro Xcv

[0204] 115. Xab Val Xab Pro Xal

[0205] 116. Xab Val Xab Pro Xam

[0206] 117. Xab Val Xab Pro Xan

[0207] 118. Xab Val Xab Pro Xao

[0208] 119. Xab Val Xab Pro Xav

[0209] 120. Xab Val Xab Pro Xaw

[0210] 121. Xab Val Xab Pro Xat

[0211] 122. Xab Val Xab Pro Xau

[0212] 123. Xab Val Xab Pro Xbf

[0213] 124. Xab Val Xab Pro Xbm

[0214] 125. Xab Val Xab Pro Xbn

[0215] 126. Xab Val Xab Pro Xbo

[0216] 127. Xab Val Xab Pro Xch

[0217] 128. Xaa Val Xab Pro Xdt

[0218] 129. Xaa Val Xab Pro Xdu

[0219] 130. Xaa Val Xab Pro Xdv

[0220] 131. Xaa Val Xab Pro Xdw

[0221] 132. Xaa Val Xab Pro Xdx

[0222] 133. Xaa Val Xab Pro Xdy

[0223] 134. Xaa Val Xab Pro Xdz

[0224] 135. Xaa Val Xab Pro Xea

[0225] 136. Xaa Val Xab Pro Xeb

[0226] 137. Xaa Val Xab Pro Xec

[0227] 138. Xaa Val Xab Pro Xed

[0228] 139. Xaa Val Xab Pro Xef

[0229] 140. Xaa Val Xab Pro Xeg

[0230] 141. Xaa Val Xab Pro Xeh

[0231] 142. Xaa Val Xab Pro Xei

[0232] 143. Xaa Val Xab Pro Xek

[0233] 144. Xaa Val Xab Pro Xel

[0234] 145. Xaa Val Xab Pro Xem

[0235] 146. Xaa Val Xab Pro Xen

[0236] 147. Xaa Val Xab Pro Xeo

[0237] 148. Xaa Val Xab Pro Xep

[0238] 149. Xaa Val Xab Pro Xeq

[0239] 150. Xaa Val Xab Pro Xer

[0240] 151. Xaa Val Xab Pro Xcg

[0241] Examples for the MS-characterization of the synthesized novel compounds are given in the following table. EXAMPLE Fast atom bombardment MS analysis. [NO.] [Mol.-Weight (measured)] 3. 565 4. 579 5. 593 6. 607 7. 621 8. 635 11. 607 12. 607 13. 621 14. 649 15. 635 16. 635 17. 635 18. 635 19. 621 20. 621 21. 635 22. 635 25. 633 26. 647 27. 661 31. 623 32. 671 33. 667 34. 631 35. 655 36. 655 37. 669 38. 621 39. 635 41. 649 42. 621 43. 633 44. 667 45. 607 46. 647 47. 668 48. 655 49. 669 50. 685 51. 629 52. 625 53. 721 55. 579 58. 623 61. 597 62. 621 63. 609 64. 625 65. 635 66. 591 67. 715 68. 685 69. 685 70. 591 71. 607 72. 621 74. 706 75. 579 76. 579 77. 579 78. 607 79. 607 80. 607 81. 607 82. 637 83. 692 84. 706 85. 706 86. 706 87. 607 90. 635 92. 659 93. 617 94. 636 95. 678 128. 671 131. 625 139. 625 151. 637

[0242] Compound Number(s) Sequence ID Number 1-56, 58-72, 75, 77, 79, 80, 82, 1 87-94, 96, 97, 99-101, 104-151 73, 74, 83-86, 95, 2 57, 76, 81, 102 3 78, 98, 103 4

[0243] Xaa: N,N-Dimethylvaline Xab: N-Methylvaline Xac:

Xad:

Xae:

Xaf:

Xag:

Xah:

Xai:

Xak:

Xal:

Xam:

Xan:

Xao:

Xap:

Xaq:

Xar:

Xas:

Xat:

Xau:

Xav:

Xaw:

Xax:

Xay:

Xaz:

Xba:

Xbb:

Xbc: N-Methyl-isoleucine Xbd:

Xbe:

Xbf:

Xbg:

Xbh:

Xbi:

Xbk:

Xbl:

Xbm:

Xbn:

Xbo:

Xbp:

Xbq:

Xbr:

Xbs:

Xbt:

Xbu:

Xbv:

Xbw

Xbx:

Xby:

Xbz:

Xca:

Xcb:

Xcc: Proline adamantyl(1)amide Xcd:

Xce:

Xcf:

Xcg:

Xch:

Xci:

Xck:

Xcl:

Xcm:

Xcn:

Xco:

Xcp:

Xcq:

Xcr:

Xcs:

Xct:

Xcu:

Xcv:

Xcw: N-Methyl-N-ethyl-valine Xcx: N,N-Diethylvaline Xcy:

Xcz:

Xda: N-Methyl-2-aminobutyroyl Xdb: 2-aminobutyroyl Xdc: N,N-Dimethyl-2-aminobutyroyl Xdd: N,N-Dimethyl-2-tert.butylglycine Xde: N,N-Dimethyl-isoleucine Xdf: 2-tert.butylglycine Xdg:

Xdh:

Xdi:

Xdk:

Xdl: N-Methyl-2-tert.butylglycine Xdm:

Xdn:

Xdo:

Xdp:

Xdr:

Xds:

Xdt:

Xdu:

Xdv:

Xdw:

Xdx:

Xdy:

Xdz:

Xaa:

Xab:

Xec:

Xed:

Xee:

Xef:

Xeg:

Xeh:

Xei:

Xek:

Xel:

Xem:

Xen:

Xeo:

Xep:

Xeq:

[0244]

[0245] Compounds of this invention may be assayed for anti-cancer activity by conventional methods, including for example, the methods described below.

[0246] A. In Vitro Methodology

[0247] Cytotoxicity was measured using a standard methodology for adherent cell lines such as the microculture tetrazolium assay (MTT). Details of this assay have been published (Alley, M C et al, Cancer Research 48:589-601, 1988). Exponentially growing cultures of tumor cells such as the HT-29 colon carcinoma or LX-1 lung tumor are used to make microtiter plate cultures. Cells are seeded at 3000 cells per well in 96-well plates (in 150 μl or media), and grown overnight at 37° C. Test compounds are added, in 10-fold dilutions varying from 10⁻⁴M to 10⁻¹⁰M. Cells are then incubated for 72 hours. To determine the number of viable cells in each well, the MTT dye is added (50 μl or 3 mg/ml solution of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide in saline). This mixture is incubated at 37° C. for 5 hours, and then 50 μl of 25% SDS, pH2 is added to each well. After an overnight incubation, the absorbance of each well at 550 nm is read using an ELISA reader. The values for the mean +/−SD of data from replicated wells are calculated, using the formula % T/C (% viable cells treated/control). ${\frac{{OD}\quad {of}\quad {treated}\quad {cells}}{{OD}\quad {of}\quad {control}\quad {cells}} \times 100} + {\% \quad {T/C}}$

[0248] The concentration of test compound which gives a T/C of 50% growth inhibition was designated as the IC₅₀ value.

[0249] B. In Vivo Methodology

[0250] Compounds of this invention were further tested in pre-clinical assay for in vivo activity which is indicative of clinical utility. Such assays were conducted with nude mice into which tumor tissue, preferably of human origin, had been transplanted (xenografted), as is well known in this field. Test compounds were evaluated for their anti-tumor efficacy following administration to the xenograft-bearing mice.

[0251] More specifically, human breast tumors (MX-1) which had been grown in athymic nude mice were transplanted into new recipient mice, using tumor fragments which were about 50 mg in size. The day of transplantation was designated as day 0. Six to ten days later, mice were treated with the test compounds given as an intravenous injection or orally, in groups of 5-10 mice at each dose. Compounds were given every other day, for 3 weeks, at doses from 1-200 mg/kg body weight.

[0252] Tumor diameters and body weights were measured twice weekly. Tumor volumes were calculated using the diameters measured with Vernier calipers, and the formula

(Length×width²)/2=mm³ of tumor volume

[0253] Mean tumor volumes are calculated for each treatment group, and T/C values determined for each group relative to the untreated control tumors.

[0254] The new compounds possess good tumor inhibiting properties. 

What is claimed is:
 1. Novel peptides of the formula I R¹R²N-CHX-CO-A-B-D-E-(G)_(s)-K  I where R¹ is hydrogen, methyl; or ethyl; R² is methyl; or ethyl; or R¹-N-R² together are a pyrrolidine ring; A is a valyl, isoleucyl, allo-isoleucyl, 2-tert-butylglycyl, 2-ethylglycyl, norleucyl or norvalyl residue; B is a N-methyl-valyl, N-methyl-norvalyl, N-methyl-leucyl, N-methyl-isoleucyl, N-methyl-2-tert-butylglycyl, N-methyl-2-ethylglycyl, or N-methyl-norleucyl residue; D is a prolyl, homoprolyl, hydroxyprolyl, or thiazolidine-4-carbonyl residue; E is a prolyl, homoprolyl, hydroxyprolyl, thiazolidine-4-carbonyl, trans-4-fluoro-L-prolyl, cis-4-fluoro-L-prolyl, trans-4-chloro-L-prolyl or cis-4-chloro-L-prolyl residue; X is ethyl, propyl, butyl, isopropyl, sec. butyl, tert.-butyl, cyclopropyl, or cyclopentyl; G is a L-2-tert.butylglycyl, D-2-terr.butylglycyl, D-valyl, D-isoleucyl, D-leucyl, D-norvalyl, 1-aminopentyl-1-carbonyl, or 2,2-dimethylglycyl residue; s is 0 or 1; K is —NH-C₁₋₈-alkyl, —NH-C₃₋₈-alkenyl, —NH-C₃₋₈-alkinyl, —NH-C₆₋₈-cycloalkyl, —NH-C₁₋₄-alkene-C₃₋₈-cycloalkyl, C₁₋₄-alkyl-N-C₁₋₆-alkyl, in which residues one CH₂ group may be replaced by O or S, one H by phenyl or cyano, or 1, 2 or 3 H by F, except the N-methoxy-N-methylamino, N-benzylamino, or N-methyl-N-benzylamino residue, or K is

and the salts thereof with physiologically tolerated acids.
 2. Novel peptides of the formula I R¹R²N-CHX-CO-A-B-D-E-(G)_(s)-K  I where R¹ is hydrogen, methyl; or ethyl; R² is methyl; or ethyl; or R¹-N-R² together are a pyrrolidine ring; A is a valyl, isoleucyl, allo-isoleucyl, 2-tert-butylglycyl, 2-ethylglycyl, norleucyl or norvalyl residue; B is a N-methyl-valyl, N-methyl-norvalyl, N-methyl-leucyl, N-methyl-isoleucyl, N-methyl-2-tert-butylglycyl, N-methyl-2-ethylglycyl, or N-methyl-norleucyl residue; D is a prolyl, homoprolyl, hydroxyprolyl, or thiazolidine-4-carbonyl residue; E is a prolyl, homoprolyl, hydroxyprolyl, thiazolidine-4-carbonyl, trans-4-fluoro-L-prolyl, cis-4-fluoro-L-prolyl, trans-4-chloro-L-prolyl or cis-4-chloro-L-prolyl residue; X is ethyl, propyl, butyl, isopropyl, sec. butyl, tert.butyl, cyclopropyl, or cyclopentyl; G is a L-2-tert.butylglycyl, D-2-terr.butylglycyl, D-valyl, D-isoleucyl, D-leucyl, D-norvalyl, 1-aminopentyl-1-carbonyl, or 2,2-dimethylglycyl residue; s is 0 or 1; K —NHCH₃, —NHCH₂CH₃, —NH(CH₂)₂CH₃, —NH(CH₂)₃CH₃, —NH(CH₂)₄CH₃, —NH(CH₂)₅CH₃, —NH(CH₂)₆CH₃, —NHCH(CH₂)₇CH₃, —NHCH(CH₃)₂, —NHCH(CH₃)CH₂CH₃, —NHCH(CH₂CH₃)₂, —NHCH(CH₂CH₂CH₃)₂, —NHC(CH₃)₃, —NHCH(CH₂CH₃)CH₂CH₂CH₃, —NHCH(CH₃)CH(CH₃)₂, —NHCH(CH₂CH₃)CH(CH₃)₂, —NHCH(CH₃)C(CH₃)₃, —NH-cyclohexyl, —NH-cycloheptyl, —NH-cyclooctyl, —N(CH₃)OCH₂CH₃, —N(CH₃)OCH₂CH₂CH₃, —N(CH₃)OCH(CH₃)₂, —N(CH₃)O(CH₂)₃CH₃, —N(CH₃)OCH₂C₆H₅, —NH(CH₂)₂C₆H₅, —NH(CH₂)₃C₆H₅, —NHCH(CH₃)C₆H₅, —NHC(CH₃)₂C₆H₅, —NHC(CH₃)₂CH₂CH₃, —NHC(CH₃)(CH₂CH₃)₂, —NHCH[CH(CH₃)₂]₂, —NHC(CH₃)₂CN, —NHCH(CH₃)CH(OH)C₆H₅, —NHCH₂-cyclohexyl, —NHCH₂C(CH₃)₃, —NHCH₂CH(CH₃)₂, —NHCH₂CF₃, —NHCH(CH₂F)₂, —NHCH₂CH₂F, —NHCH₂CH₂OCH₃, —NHCH₂CH₂SCH₃, —NHCH₂CHCH₂, —NH-C(CH₃)₂CH═CH₂, —NHC(CH₃)₂C≡CH, —NHC(CH₂CH₃)₂C≡CH, —NHC(CH₃)₂CH₂CH₂OH, —NH(CH₂CH₂O)₂CH₂CH₃, —NHC(CH₃)₂CH(CH₃)₂, —NHC(CH₃)₂CH₂CH₂CH₃, —NHC(CH₃)₂CH₂C₆H₅, —N(OCH₃)CH(CH₃)₂, —N(OCH₃)CH₂CH₃, —N(OCH₃)CH₂CH₂CH₃, —N(OCH₃)CH₂C₆H₅, —N(OCH₃)C₆H₅, —N(CH₃)OC₆H₅, —NHCH[CH(CH₃)₂]₂, —N(OCH₃)CH₂CH₂CH₂CH₃, or K is

And the salts thereof with physiologically tolerated acids.
 3. Novel peptides of the formula I R¹R²N-CHX-CO-A-B-D-E-(G)_(s)-K  I where R¹ is hydrogen, methyl; or ethyl; R² is methyl; or ethyl; A is a valyl, isoleucyl, 2-tert-butylglycyl, 2-ethylglycyl, norleucyl or norvalyl residue; B is a N-methyl-valyl, N-methyl-norvalyl, N-methyl-isoleucyl, N-methyl-2-tert-butylglycyl, N-methyl-2-ethylglycyl, or N-methyl-norleucyl residue; D is a prolyl, or thiazolidine-4-carbonyl residue; E is a prolyl, homoprolyl, thiazolidine-4-carbonyl, trans-4-fluoro-L-prolyl, cis-4-fluoro-L-prolyl, trans-4-chloro-L-prolyl or cis-4-chloro-L-prolyl residue; X is ethyl, propyl, isopropyl, sec. butyl, tert.-butyl, or cyclopropyl; G is a L-2-tert.butylglycyl, D-2-terr.butylglycyl, D-valyl, D-isoleucyl, D-leucyl, or 2,2-dimethylglycyl residue; s is 0 or 1; K is —NH-C₁₋₈-alkyl, —NH-C₆₋₈-cycloalkyl, —NH-CH₂-cyclohexyl, C₁₋₄-alkyl-N-C₁₋₆-alkyl, in which residues one CH₂ group may be replaced by O, one H by phenyl or 1 or 2 H by F, except the N-methoxy-N-methylamino, N-benzylamino or N-methyl-N-benzylamino residue, or K is


4. Novel peptides of the formula I R¹R²N-CHX-CO-A-B-D-E-(G)_(s)-K  I where R¹ is methyl; R² is methyl; A is a valyl, isoleucyl, 2-tert-butylglycyl, or 2-ethylglycyl; B is a N-methyl-valyl, N-methyl-isoleucyl, N-methyl-2-tert-butylglycyl, N-methyl-2-ethylglycyl, or N-methyl-norleucyl residue; D is a prolyl, or thiazolidine-4-carbonyl residue; E is a prolyl, trans-4-fluoro-L-prolyl, cis-4-fluoro-L-prolyl, trans-4-chloro-L-prolyl or cis-4-chloro-L-prolyl residue; X is ethyl, isopropyl, sec. butyl, or tert.butyl; G is a L-2-tert.butylglycyl, D-2-terr.butylglycyl, D-valyl, D-isoleucyl, D-leucyl, or 2,2-dimethylglycyl residue; s is 0 or 1; K is —NH-C₁₋₈-alkyl, —NH-C₆₋₈-cycloalkyl, —NH-CH₂-cyclohexyl, C₁₋₄-alkyl-N-C₁₋₆-alkyl, in which residues one CH₂ group may be replaced by O, one H by phenyl or 1 or 2 H by F, except the N-methoxy-N-methylamino, N-benzylamino or N-methyl-N-benzylamino residue, or K is


5. Novel peptides of the formula I R¹R²N-CHX-CO-A-B-D-E-(G)_(s)-K  I where R¹ is methyl; R² is methyl; A is a valyl, isoleucyl, or 2-tert-butylglycyl residue; B is a N-methyl-valyl, N-methyl-isoleucyl, or N-methyl-2-tert-butylglycyl residue; D is a prolyl, or thiazolidine-4-carbonyl residue; E is a prolyl, cis-4-fluoro-L-prolyl or cis-4-chloro-L-prolyl residue; X is isopropyl, sec. butyl, or tert.-butyl; s is 0 or 1; K is —NHC(CH₃)₃, —NHCH(CH₂CH₂)CH(CH₃) ₂, —NHCH(CH₃)C(CH₃)₃, —N(CH₃)OCH₂CH₃, —N(CH₃)OCH₂CH₂CH₃, —N(CH₃)OCH(CH₃)₂, —N(CH₃)O(CH₂)₃CH₃, —N(CH₃)OCH₂C₆H ₅, —NHC(CH₃)₂C₆H₅, —NHC(CH₃)₂CH₂CH₃, —NHC(CH₃)(CH₂CH₃)₂, —NHCH[CH(CH₃)₂]₂, —NHC(CH₃)₂CN, —NHCH(CH₃)CH(OH)C₆H₅, —NH-C(CH₃)₂CH≡CH₂, —NHC(CH₃)₂C≡CH, —NHC(CH₂CH₃)₂C≡CH, —NHC(CH₃)₂CH₂CH₂OH, —NHC(CH₃)₂CH(CH₃)₂, —NHC(CH₃) ₂CH₂CH₂CH₃, —NHC(CH₃)₂CH₂C₆H₅, —N(OCH₃)CH(CH ₃)₂, —N(OCH₃)CH₂CH₃, —N(OCH₃)CH₂CH₂CH₃, —N(OCH₃)CH₂C₆H₅, —N(OCH₃)C₆H₅, —N(CH₃)OC₆H₅, —N(OCH₃)CH₂CH₂CH₂CH₃, or K is

and the salts therof with physiologically tolerated acids.
 6. Novel peptides of the formula I R¹R²N-CHX-CO-A-B-D-E-(G)_(s)-K  I where R¹ is methyl; R² is methyl; A is a valyl residue; B is a N-methyl-valyl residue; D is a prolyl residue; E is a prolyl residue; X is isopropyl; s is 0 or 1; K is —NHC(CH₃)₃, —NHCH(CH₂CH₂)CH(CH₃)₂, —NHCH(CH₃)C(CH₃)₃, —N(CH₃)OCH₂CH₃, —N(CH₃)OCH₂CH₂CH₃, —N(CH₃)OCH(CH₃)₂, —N(CH₃)O(CH₂)₃CH₃, —N(CH₃)OCH₂C₆H₅, —NHC(CH₃)₂C₆H₅, —NHC(CH₃)₂CH₂CH₃, —NHC(CH₃)(CH₂CH₃)₂, —NHCH[CH(CH₃)₂]₂, —NHC(CH₃)₂CN, —NHCH(CH₃)CH(OH)C₆H₅, —NH-C(CH₃)₂CH═CH₂, —NHC(CH₃)₂C≡CH, —NHC(CH₂CH₃)₂C≡CH, —NHC(CH₃)₂CH₂CH₂OH, —NHC(CH₃)₂CH(CH₃)₂, —NHC(CH₃)₂CH₂CH₂CH₃, —NHC(CH₃)₂CH₂C₆H₅, —N(OCH₃)CH(CH ₃)₂, —N(OCH₃)CH₂CH₃, —N(OCH₃)CH₂CH₂CH₃, —N(OCH₃)CH₂C₆H₅, —N(OCH₃)C₆H₅, —N(CH₃)OC₆H₅, —N(OCH₃)CH₂CH₂CH₂CH₃, or K is

and the salts thereof with physiologically tolerated acids.
 7. Novel peptides of the formula I R¹R²N-CHX-CO-A-B-D-E-(G)_(s)-K  I where R¹ is methyl; R² is methyl; A is a valyl, isoleucyl, or 2-tert-butylglycyl residue; B is a N-methyl-valyl, N-methyl-isoleucyl, or N-methyl-2-tert-butylglycyl residue; D is a prolyl, or thiazolidine-4-carbonyl residue; E is a prolyl residue; X is isopropyl, sec. butyl, or tert.-butyl; G is a D-2-tert.butylglycyl, D-isoleucyl, 2,2-dimethylglycyl residue, D-valyl or L-2-tert.butylglycyl; s is 1; K is —NHCH₃, —NHCH₂CH₃, —NH(CH₂)₂CH₃, —NH(CH₂)₃CH₃, —NH(CH₂)₄CH₃, —NH(CH₂)₅CH₃, —NHCH(CH₃)₂, —NHCH(CH₃)CH₂CH₃, —NHCH(CH₂CH₃)₂, —NHC(CH₃)₃, —NH-cyclohexyl, —NHC(CH₃)₂CN, —NCH(CH₃)₂C≡CH or —NHC(CH₃)₂CONH₂; or K is

and the salts thereof with physiologically tolerated acids.
 8. Compounds of formula I or salts thereof for use in treating diseases.
 9. The method or preparing compounds of formula I according to claim 1 characterized in that they are prepared according to known methods of peptide chemistry. 